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If the sun expands?

  1. Feb 3, 2010 #1
    Hello! I'm new here, and I don't honestly know anything about astrophysics, so I'm sorry in advance for the upcoming questions and would like to ask you to be as elaborate and as simple as possible.
    So, if the sun expands, when do you think this will happen? If Earth is still alive, what do you think humans would do? Would we potentially have the technology to save our world, simply change locations?
    Please share your theories:)
  2. jcsd
  3. Feb 3, 2010 #2


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    The Sun is not expected to expand (significantly) for another 4-5 billion years, when it will turn into a Red giant.

    The Red giant may very well engulf the Earth, since it may expand to sizes larger than the Earth's orbit. The Earth may escape this fate, if the loss in mass of the sun is enough to let the Earth orbit farther out. This is uncertain.

    Long before that, though, the Sun would have dried out the Earth, since it's getting hotter and hotter. The Oceans will boil in ~ 1 billion years. Human's have about that much time to find something to do.
  4. Feb 4, 2010 #3
    I think as long as we persue the exploration of space we will have left Earth long before the Sun dies. We may even discover ways to produce our own energy and not have need of a star.
  5. Feb 4, 2010 #4
    As all ready mentioned here.

    Long before the Sun goes to the Red Giant stage we should have learned how to control vast amounts of energy and have developed technology that today hasn’t even been thought of.

    That is of course, provide we haven’t succumb to some sort of catastrophic event or worse yet rendered ourselves extinct.

    I think when that time comes there will be at least a few options and they will probably have the technology to deal with it or perhaps even have dealt with it long before it occurs.

    Sort of ironic as the sun expands some of the outer planets will warm and actually for a certain time become conducive to life. However, it will be a short lived period.
  6. Feb 4, 2010 #5
    You said that last time.

    Hard to tell. The Sun's Main Sequence lifespan depends on its core metallicity and the Main Sequence might end when it's somewhere between 9 and 11 billion years old.

    However that's assuming it's not accreting significant amounts of dark matter. If dark matter built up and increased the Sun's mass significantly then it would burn faster and leave the Main Sequence earlier.

    Re-engineering the Sun might eventually be possible. Only its core is being depleted in hydrogen presently - if we can cause the Sun's mass to convect, then we might be able to cause its lifespan to increase significantly. Otherwise we might need to lift mass off it and control the core indirectly that way.

    Maybe, but why bother? A shell around the planet with variable albedo would reduce the influx of heat sufficiently to keep it habitable. However if the Sun is sucking up dark matter at a great rate, then we'll probably have to do something about moving the planet eventually. If the Sun retains it sufficiently well, then the Sun might eventually exceed the Chandrasekhar Mass and go supernova - though that's less urgent than an accelerated Main Sequence.

    What cut do I get from your novel or whatever it is you're working on?
  7. Feb 5, 2010 #6


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    It does not appear dark matter will be a factor in the evolution of the sun. The amount currently present in the solar system is estimated at around 10% the mass of the asteroid Ceres - re:
    Dark Matter in the Solar System
  8. Feb 5, 2010 #7
    Maybe, maybe not. Lorenzo Iorio disagrees with your extrapolation in this (more recent) paper...

    http://arxiv.org/abs/1001.1697" [Broken]

    ...and since nuclear fusion rates are rather sensitive to pressure in the Core I would suggest the mass accreted will have significance in the gigayears ahead.
    Last edited by a moderator: May 4, 2017
  9. Feb 7, 2010 #8
    Spoiler Alert!!!!!

    Humanity will not be there to see it. :rofl:
  10. Feb 7, 2010 #9
    If humanity survives long enough to see the Earth being threatened by the sun, we'd have long since spread across the universe. Saving the Earth would be like saving the great pyramids - historically important, but hardly a threat to our survival.

    Planets can be moved by sending lots of asteroids on close encounters. Their gravity would (slowly!) pull the Earth in whatever direction required.

    I wonder if you could cover large sections of the Earth with mirrors and create something like a solar sail? That would cool the Earth, and push it away from the sun.
  11. Feb 7, 2010 #10
    Given the amount of time we're talking about, it's hard to imagine any form of life persisting for such a long period; there is nowhere near the that kind of precedent. If you consider our history, there is only one safe bet, and it isn't on us.

    All the more reason to enjoy these intellectual exercises... life is one after all is said and done. We'll all be ashes in an expanding gas cloud, dimly lit by the heat trapped in the degenerate electron matter that was The Sun, fading as the universe expands and the cosmological horizon changes so radically that humans then wouldn't have a reason for attatchment to any particular stellar grouping. The 'long run' is never really happy after all. :biggrin:
  12. Feb 7, 2010 #11
    Personally I suspect that whatever lives then will - however distantly - be related to us, and might welcome some long-term thinking by their ancestors. But the struggle for survival might prove tougher if Dark Matter influences stellar evolution as dramatically as Iorio's computations imply.
  13. Feb 7, 2010 #12
    GIANT ROBOTS! They will be our decedents. But since they were originally created to serve us, they will keep us as pets and take us to breeding shows. The winner will have a capitlistic society in a box and the young robots will gather around and say "Look at the little humans they are so cuuuute!"
  14. Feb 7, 2010 #13
    Do you look to our ancestors of millions of years past for their thinking on ANY subject, for any but academic curiosity? Given our burgeoning ability to modify ourselves, I doubt that any descendant of humanity would resemble it in any way. Forget evolution... we'll change ourselves to suit conditions before we change the world to suit us in more than the crude ways we already do.

    If FTL isn't to be achieved, then descendants will be cut off from their pasts by the very act of setting out on an intersellar journey; moreso if they travel near c. I think the key to life is in the setting we can comprehend as humans, limited, but one to which we are adapted. To pretend that we can imagine the world of a million or a billion years from now is fanciful, but understandable.
  15. Feb 7, 2010 #14
    "Can I pet the little humans pleeease???"

    "No dear, if they find out they aren't in charge they get sick."
  16. Feb 7, 2010 #15
    :rofl: I think that's more near-term than long-term lol.
  17. Feb 7, 2010 #16
    I'm going to go eat some cooked meat while wearing clothing that compensates for my lack of fur. :)
  18. Feb 7, 2010 #17
    Yes, well... point taken. Damn. Still, do you really think that given the pace of progress we'll have so much in common with our descendants seperated by a similar span of time? I don't think so, but you've made some very good points.

    Given the advent of computer-human interfaces, and genetic modification (yes, a matter of time, but if we're to survive it probably will emerge), micro/nano technology... I don't know. I don't know enough about what it means to be human, or conscious to imagine how our descendants might shape themselves according to answers to those great questions.

    If consciousness can be transferred digitally (or by some other means), that would have implications for the necessity of a physical existence outside of a 'blue box'. If physical modifications are the main trend because unique personal traits are linked to your brain, and can't be transferred.... who knows.

    It's not fair that so many questions exist in so many fields, and that we'll only ever know a miniscule fraction of the answers. Most of the time we're all just trying to find the right questions to ask in the first place, or just how to ask it. Our lifespans and society continually disrupt steady progress. Very upsetting.
  19. Feb 8, 2010 #18


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    Nanobots encoded with our DNA is a viable option for preserving the human race. It is an unromantic and desperate measure, but, within the grasp of believable physics and technology.
  20. Feb 8, 2010 #19
    Nanobots encoded with our DNA are called "ova" and usually require a womb to produce a human being from them. Otherwise the DNA is just a random bit string. It needs a context to be understood.
  21. Feb 8, 2010 #20
    Within the grasp of current psychology I would question whether humanity at any stage would take such a long view. In a way, that view is deeply inhuman. When we're gone... we'll be gone.
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